Improved removal of dyes by [sodium alginate/4-methyl-2-(naphthalen-2-yl)-N-propylpentanamide-functionalized ethoxy-silica] composite gel beads

Abstract

In this paper, the synthesis of [sodium alginate/4-methyl-2-(naphthalen-2-yl)-N-propylpentanamide-functionalized ethoxy-silica] composite gel beads is described. The characterizations were carried out using Fourier Transform InfraRed, Scanning Electron Microscopy, point zero charge and water content. The morphology of the alginate gel beads are changed after functionalization and are characterized by aggregates of different sizes and irregular shapes. The adsorption is checked for Methylene Blue and Acid Blue 25 in batch mode with reference to the change of pH, time, temperature, and adsorbate concentration. A reliance on the studied experimental conditions is observed. The sorption capacities were improved using composite gel beads compared to gel beads. A possible complex formation of composite gel beads and the studied adsorbates is proposed. The kinetic data complies well with the second order. The intra-particular Diffusion exhibits the existence of two successive adsorption stages of mass transport. The data fitted with Freundlich indicate that the adsorption might occur in the heterogeneous adsorption sites. The prepared beads are considered moderate for the removal of the dyes (n > 1). The negative value of enthalpy (−23.7 < ΔH* < −7.14) confirms that the process is exothermic which is, also, supported by the decrease of the adsorption energy constants (B) of Temkin model.